A Novel Method for DC Fault Identification and Localization Based on Parallel Energy Absorption Module in Auto-Reclosing of MMC-HVDC Systems

The most challenging issue in high voltage direct current (HVDC) systems in terms of protection is the DC-side fault, which should be interrupted quickly. In addition to fault current clearance, safe reclosing of the HVDC system is essential. Otherwise, a second strike can endanger the system components as semiconductor devices in modular multilevel converters and DC circuit breakers (DCCBs) are vulnerable to another high current. In this paper, a new method for DC fault identification and localization in auto-reclosing of the HVDC system is proposed, in which an energy absorption module added to a hybrid DC circuit breaker is used to reach these objectives. In the proposed approach, a mechanical switch in the energy absorption module provides a path for discharge of its capacitor into the line, which helps to get valuable information about the type of the fault and its location by the characteristics of the discharge waveform. The effectiveness of the proposed method is validated by a point-to-point HVDC test system based on modular multilevel converters built in PSCAD/EMTDC platform, and curve fitting toolbox in MATLAB software. The simulation results confirm that the proposed method has no identification dead zone and is robust to fault resistance. Moreover, it does not affect other parts of the system.